The application of heat-shrinkable plastic labels to bottles and the subsequent movement of the bottles through a heat-shrink oven has been the subject of a number of issued patents and pending patent applications.
For example, U.S. Pat. No. 3,802,942, dated Apr. 9, 1974, discloses the process of forming a sleeve from a supply of heat-shrinkable, foamed polystyrene and assembling the sleeve over the body of a glass container with the subsequent movement of the container through an oven to heat-shrink the sleeve into conforming relationship to the container. The sleeve may be preprinted and serves as the label for the container. It should be noted that the necessity of preheating the bottle is explained and that the container, which is supported by its neck, first passes through a preheat oven before having the sleeve applied thereto. The sleeve is formed by heat sealing its overlapping ends.
In another U.S. Pat. No. 4,671,843, dated June 9, 1987, a strip of heat-shrinkable, label material is applied in a wraparound manner to the bottles with the body of the bottle serving as the mandrel for forming the sleeve on the bottle. In this patent the subsequent passage of the bottle through a shrink oven completes the formation of a label that is heat-shrunk about the bottle side wall between the heel and shoulder thereof. The overlapping ends of the label are sealed to each other by the use of a solvent for the plastic of the label.
It has been found that in those situations where the bottles are used as the mandrel as in the case of U.S. Pat. No. 4,671,843, the subsequent heat-shrinkage of the label is not satisfactory where more than a 20% shrinkage of the label is required. When more than a 20% shrinkage was required, as is the case with the "family size" container, wrinkles would appear due to uneven shrinkage of the label.
With the foregoing in view, it is an object of the present invention to provide an effective preheat system for the glass bottles before the shrink labels are formed thereon so that a wrinkle-free label will be formed.
It is an additional object of this invention to provide a preheat system for glass containers which is relatively simple in its operation and effective to preheat the bottles from 100.degree. F. to 140.degree. F. while being fed at a rate of up to 600 bottles per minute with at least a 90.degree. rotation of the bottles during the preheat operation.
Other and further objects will be apparent from the following description taken in conjunction with the annexed sheets of drawings.